Classical large image databases, such as those used by Google Earth and Microsoft Virtual Earth, require map data to be preprocessed. As a result, only one set of map data is served up with only one view into the map data. This limits the ability to rapidly make new map data available or to view map data from different perspectives, for example, viewing changing map data over time.
Current systems use a Web Mapping Service (WMS) with a WMS data layer that could include some cache system. In most systems, scalability and performance are enhanced by adding additional image services and using various load balancing techniques. For example, any users as clients could be connected by the internet to the WMS as one or more servers that could be load balanced with other WMS servers and a shared database such as a retrieval and information database. Performance can be enhanced by preprocessing imagery, trading currency of data for response time. Some systems have many tiles assembled at the client in which tiles are already predefined such that a client will fetch a tile, thus placing much work on the client with excessive map data processing occurring at the client.